[calmpeach]

Hi all!

I would really appreciate your help - I'm not great at dilutions I have had a try at this but it's probably not right lol. It would be very helpful if you could include how you worked it out as well as the rationale behind each calculation!

Reagents:

• Mr of drug: 270.241 (synthetic powder, ≥98% (HPCL)) - 5mg
• 100% ethanol
• Deionised water

Requirements:

• Dissolve drug in 80% hot (60C) ethanol - highest solubility in a solvent I can work with
• Injection is of 10 ul at a drug concentration of 100 uM
• The concentration of ethanol in the final injection has to be 10%
• This is a pilot study so I would like to use as little as possible of the drug to conduct probably ~15 of the initial 10 ul, 100uM doses
• I would also have to work with 10 uM, 1 uM concentrations so dilutions are required

Initial thought:

• Dissolve x amount of powder in x volume of 80% hot ethanol to yield a concentration that is higher than 100 uM
• Dilute this down with deionised water so ethanol is at 10% and the drug is at 100 uM

Not sure how to go about this.. 

[the inquisitor]

Firstly, decide on mL (ethanol + water) to be used for your 80% ethanol solution and then calculate by how much you would have to dilute this solution to arrive at a 10% ethanol solution.

Might be useful here:
C1V1 = C2V2

V1 = Volume of stock solution needed to make the new solution
C1 = Concentration of stock solution
V2 = Final volume of new solution
C2 = Final concentration of new solution

Secondly, calculate the amount of drug required to be added as per the final volume of your 10% ethanol solution.